It is known that when a vehicle such as a caravan or camper trailer or the like is being towed by a towing vehicle such as a car or truck or the like, the towed vehicle has an inherent tendency to become unstable by swaying or fishtailing, which creates a hazardous condition for driving. The tendency of the towed vehicle to sway is initiated and amplified by uneven weight distribution and driving conditions including speed, braking, prevailing wind and rain, and even passing or being passed by other vehicles on the road.
There have been many reported accidents and roll-overs as a result of loss of control of the towing vehicle steering due to uncontrollable sway of the caravan or trailer. One way of trying to minimise swaying of a towed vehicle when towing, has been to use a friction sway control device. The sway control device includes a metal plate, on which is a small ball mount, that can be bolted onto the a frame or draw bar of a caravan or trailer. The hitch receiver can be modified by welding on a small ball mount for the other end of the sway control bar to attach. While this type of sway control device is practical for correcting minor sway of a towed vehicle by varying weight distribution when towing, further improvements or alternative means are required to address potential loss of control arising from dangerous and/or excessive sway.
National towing regulations exist in many jurisdictions now which make it mandatory for all towed vehicles such as caravans, camper trailers and the like with an aggregate trailer mass (including load) over 750 kg to have an effective braking system fitted. It is not unusual for caravans exceeding 1000 kgs to be fitted with electric brakes.
In order to operate electric trailer brakes, an electric brake controller is installed in the towing vehicle. In a towing condition, power is supplied from the towing vehicle battery to the electric brake controller, and the controller is also wired to the towing vehicle's stop light circuit through the towed vehicle's plug and socket. This allows the towed vehicle's brakes to come on automatically when the towing vehicle brakes are applied so that when a towing vehicle slows down under braking, the electric brakes on the caravan can be applied in proportion to reduce the effect of the (weight of the) caravan pushing the towing vehicle.
One problem with this is that while an electric brake controller can assist to minimise the effect of a towed vehicle mass on the operation of a towing vehicle under braking conditions, there is a need to provide a system which can operate the towed vehicle's brakes independent from the towing vehicle's brakes so as to manage an unstable conditions caused by swaying of the towed vehicle.
Some electric brake controllers have included a manual over ride systems which allow a driver to manually adjust the level of power to the electric brakes. One practical problem with this however is that a driver first has to identify an unstable towing condition and then operate the controller to apply an effective braking force. This has the potential to increase instability while braking, and in practice there is usually a delay which may allow an unstable condition to worsen.
While electric brake controllers have gone some way toward addressing problems associated with proportional pushing forces exerted by a towed vehicle on a towing vehicle during braking, there still remains the practical issues of swaying and oscillation caused by road conditions such as wind, slippery road surfaces or even pressure variations when passing another vehicle, which could have catastrophic consequences.
Further, electric brake controllers are usually fitted under a dash board element of a towing vehicle so as to be within reach of a driver. A problem with electric brake controllers is that most newly manufactured vehicles now include knee airbags to protect the knees of the driver, and the location of controllers will interfere with the normal operation of the knee airbag.
It is therefore an object of the present invention to address one or more of the foregoing problems. In particular an object of the invention is to provide an alternate device or system for improving sway stability of a towed vehicle when being towed substantially independently of the towing vehicle.